1. FIELD OF THE INVENTION: This invention relates to a subsurface well tool for use in oil and gas wells, for use in injecting fluids into perforations within the well bore; more specifically, to a well tool mechanically set by manipulation of a tubing string, and providing for pressure equalization across packing elements on opposite sides of a perforation to facilitate release of the well tool.
2. DESCRIPTION OF THE PRIOR ART: It is often necessary to inject fluids, such as water, acid, or various types of chemicals, into an underground formation through perforations in the casing which provides for communication between the formation and the well bore. Most conventional injection tools can be used to inject fluids into the perforations contained within a specified interval of a well. Normally these tools require the use of two tools, one above the interval and one below the interval, connected together to permit fluid injection. Thus, a packer can be secured to a ported tubing section which is in turn secured to a lower packer, thus, providing isolation for the intermediate interval. However, these tools are suitable only for injecting fluids into intervals of six feet or greater. These tools generally are not suitable for injecting fluids into intervals as small as six inches, which may be desirable if fluids must be selectively injected into closely adjacent perforations. The conventional multipacker device is unsuitable for use in injecting fluids into such small intervals, because the mechanism necessary to set each packer renders it virtually impossible to position the packers closely adjacent each other.
One tool which can be used to inject fluids into a well is a modified version of the tool shown in U.S. Pat. No. Re. 25,639. As depicted in that patent, the packer shown therein would not be suitable for radial injection through the tubing string and out the mandrel. However, a radially extending mandrel port has been employed on tools similar to that shown in U.S. Pat. No. Re. 25,639 to accommodate such fluid injection